mmap: call unlink_anon_vmas() in __split_vma() in case of error

If __split_vma fails because of an out of memory condition the
anon_vma_chain isn't teardown and freed potentially leading to rmap walks
accessing freed vma information plus there's a memleak.

Signed-off-by: Andrea Arcangeli <[e-mail]>
Acked-by: Johannes Weiner <[e-mail]>
Acked-by: Rik van Riel <[e-mail]>
Acked-by: Hugh Dickins <[e-mail]>
Cc: Marcelo Tosatti <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/mmap.c

···
 			removed_exe_file_vma(mm);
 		fput(new->vm_file);
 	}
+	unlink_anon_vmas(new);
  out_free_mpol:
 	mpol_put(pol);
  out_free_vma: